1.In a large, heavy-based saucepan, combine stock, lemongrass, palm sugar, garlic and star anise. Bring to boil on high. Add wontons and simmer 3-4 minutes.
2.Divide bok choy, noodles, wontons and duck between bowl. Ladle soup over. Add fish sauce.
3.Top with green onion and chilli. Serve with fresh lime.
If Peking duck is unavailable, use barbecued chicken instead. Palm sugar, usually sold in hard cakes and grated for cooking, is available from Asian food stores. If unavailable, use brown sugar.